A DRAM tends to have high cell density, which causes row hammer problems to occur. When a row of the DRAM is repeatedly activated, charges of the row may leak and interact electrically with an adjacent row, causing the adjacent row, which is not desired to be activated, to experience a bit flipping phenomenon. Generally, a row that suffers from a row hammer problem is regarded as a stressed row.
One way to solve the row hammer problem is to refresh the stressed row. However, most conventional methods to refresh the stressed row have low refreshing efficiency.
This Discussion of the Background section is for background information only. The statements in this Discussion of the Background are not an admission that the subject matter disclosed in this section constitutes a prior art to the present disclosure, and no part of this section may be used as an admission that any part of this application, including this Discussion of the Background section, constitutes prior art to the present disclosure.